Kick a two hundred pound sand bag with the blade of your foot then with your heel. You'll figure out which one works in about two seconds.

Exactly. Though I was first of all taught the blade version I had seen myself that it was no use hitting with the side of the foot except you are into some ankle injuries.
However if you are fighting on the street with your shoes on, blade style might be of use, that is still very little though. It would deflect your opponent's attention for a second so that you could punch him etc..
Otherwise I am all for the heel kick. Especially kicking downward to the knee. this's a crushing stomping effect.

I find that when kicking the bag with the heel, it swings farther. But it is more of a push than a strike. When i kick with the blade, the bag kind of bounces up and down, which is a good thing.

That just means you need to work on speed/explosive power in your kicks more.

One reason blade kicks are so popular is they can usually be thrown faster and higher with less effort. And we all know that it doesn't matter how much power is actually delivered with a kick, just whoever makes contact first wins - right? Another reason I believe point sparring was created by Satan.

I hate to post this but in the cause of full disclosure, back in my TKD days I saw guys drilling on the pad using the blade of the foot, we where never taught it any other way as far as I can remember. I did see one particularly memorable accident where a pad holder was holding a pad to low and the kicker kicked too high, the foot glanced of the pad, hit the holder in the chest then actually did slide up and catch the guy full in the throat even though he was pulling his head in as it happened, the blow knocked the pad holder unconscious.

How likely it is you'll be able to do that on a repeatable basis against someone who isn't standing their holding a pad incorrectly I don't know but the blade of the foot hing isn't complete BS.

Okay here are my two cents to the issue.
Usually you are supposed to hit with the heel in order to do that in TKD (not any more) it was told to form a blade with the foot and then turn it that your toes somewhat towards the ground (kind of like a dollyochagi only without your toes pulled back and more downward). Since most people are lazy when it comes to technique and flexibility they changed that and only turned the foot until it was parallel to the ground.

I added two pictures one of the "old" and one of the "new" version. (If you have any issues with the pictures I tell you it is a pain in the ass to do a jopchagi and hold a DSLR taking a picture in the mirror)

I hate to post this but in the cause of full disclosure, back in my TKD days I saw guys drilling on the pad using the blade of the foot, we where never taught it any other way as far as I can remember. I did see one particularly memorable accident where a pad holder was holding a pad to low and the kicker kicked too high, the foot glanced of the pad, hit the holder in the chest then actually did slide up and catch the guy full in the throat even though he was pulling his head in as it happened, the blow knocked the pad holder unconscious.

How likely it is you'll be able to do that on a repeatable basis against someone who isn't standing their holding a pad incorrectly I don't know but the blade of the foot hing isn't complete BS.

I don't know enough to say whether or not it is complete bullshit, but I would argue that no single incident can establish it; flukes do happen, but extremely low-percentage techniques are pretty much bullshit, even if they can sometimes work -- eye gouges, flying double armbars, wrist-grabby and finicky twisty techniques from aikido, those lunge punches I wasted so much time doing thousands of repetitions of in karate...

Even t3h d34dly throat strike isn't automatically lethal, after all. Where's that thread where posters were saying that "Yeah, getting punched hard in the throat during sparring sucked, but I kept going"...?

How likely it is you'll be able to do that on a repeatable basis against someone who isn't standing their holding a pad incorrectly I don't know but the blade of the foot hing isn't complete BS.

Hitting him on the chest with a Jopchagi knocking him out, hitting him on the chest, then sliding upwards and knocking him out or just hitting him in the throat to knock him out?
For the chest KO I have been hit hard and it knocked the wind out of me and stuff but never rendered me unconscious.
The hitting him on the chest and slide up, very unlikely to almost impractical since I guess he did not hit him in the throat but under/on the chin (there are some nice knockout points) and it is very hard to generate enough power after moving forward into his chest and then upwards hitting him in the chin.
If he just went over the pad and hit him under the chin (which I believe is what happened) in an upward motion it is very likely and can be achieved with some proper kick training, I have seen this happen in two fights one against a guy from my dojo he was out for like half a minute and "dizzy" for the rest of the day.